Understanding accelerometer data

Michael Tansella michael-tansella at gmx.de
Thu Oct 29 23:40:22 CET 2009

Am Donnerstag, 29. Oktober 2009 23:16:53 schrieb Robin Paulson:
> 2009/10/30 Neil Jerram <neiljerram at googlemail.com>:
> > I'd expect the x and y values to be much smaller than the z values
> > (compared to the ratios here) because of the z value including
> > gravity.  Am I misunderstanding what the data is telling me?
> yes. acceleration is change of velocity. if there is no change in
> velocity, there will be no acceleration. hence, if the phone is still,
> all acc values should be zero. gravity or not, there is no net acc on
> the phone. i don't know the format the accelerometers output data in,
> but i'd take a punt that the values shown are noise. try running one
> of the acc scripts on the wiki and going for a walk/run/climbing
> steps/waving it around/car ride with it, to see what sort of acc
> values you can get for different activities

If the Freerunner is not moving (x^2+y^2+z^2)^(1/2) must be g. The values of 
the freerunner are in mg so it must be 1000.

Your values are really strange. Do the x values never change?

I would recommend the python script for easy testing:


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